There are several known processes for the enrichment of valuable non-sulfidic minerals from ground crude ores by flotation. Valuable minerals of this type are, for example, apatite, fluorite, scheelite and other salt-like minerals, cassiterite and other heavy-metal oxides, for example those of titanium and zirconium, and certain silicates and aluminium silicates which are floated, for example in the presence of so-called collectors. In many cases, the collectors used are fatty acids, particularly unsaturated fatty acids, such as oleic acid. Other suitable collectors are, for example, sulfonate surfactants, such as alkyl aryl sulfonates, sulfosuccinic acid monoalkyl esters or alkyl or aryl phosphonates.
However, collectors such as these based on fatty acids or sulfonates are known to be comparatively non-selective because they are also suitable for the flotation of silicate-containing and carbonate-containing minerals and, for this reason, are of only limited use in cases where accompanying minerals such as these have to be separated off from other valuable minerals. Accordingly, other aids or complicated mixtures of reactants have to be added to depress the undesirable gangues. Consequently, technical problems are presented; in particular, when selective flotation is carried out in the presence of calcite as gangue, the use of fatty acids or collectors containing sulfo groups results in significant practical disadvantages.